Aircraft and water vessels (“craft”) containing on-board electronics can require accessible water-tight compartments to house, for example, on-board electronic components. As employed herein, the term “water-tight” is understood to refer to resistance to diffusion or flow of liquid or gas molecules through a boundary or envelope, the gas being oxygen or air, or the liquid being water, for example. Such a water-tight compartment typically is enclosed by a water-proof envelope, and includes a removable hatch that is tightly fastened over the top of the compartment. It is desirable that the hatch may be removed and re-installed repeatedly, while attaining a water-tight or air-tight seal with the compartment upon each re-installation. The outermost surface of the hatch is typically flush with the outer surface of the craft, to present an aerodynamically smooth overall surface. Such a water-tight compartment may have conduits passing between the interior of the water-tight compartment and other locations on the craft external of the water-tight compartment. Each conduit may accommodate various wires, fiber optic cables and tubes. This enables communication between the electronics contained inside the water-tight compartment and other elements on the craft. Each such conduit must penetrate the water-proof envelope of the water-tight compartment, and therefore entails a risk of leakage around the interface between the conduit and the water-proof envelope. This is particularly true in cases where a water landing cools the interior of the water-tight compartment, thereby creating a vacuum that pulls moisture in through any small voids that may exist at the interface between the water-proof envelope and any of the conduits passing through the water-proof envelope. Such problems can be addressed by using a special mechanical seal fitting at each one of the conduits. Such an approach may be undesirable due to the complexity, cost and weight entailed in such mechanical seal fittings. What is needed is a way of preventing leakage through the water-tight envelope around the various conduits without requiring special mechanical seal fittings.